From Xojo Documentation
Returns the index of the first element of the array.
result = array.FirstIndex
|result||Integer||The starting index of the array.|
|array||Array of any data type||The array whose first element number you want.|
The FirstIndex function is used to determine the first element of an array. This is especially useful for writing code that loops through arrays so that you don't have to be aware of whether an array begins at 0 or 1 (they all begin at 0).
Arrays can have a maximum index value of 2,147,483,646.
This code loops through an array and replaces each occurrence of X in an array with Y.
If names(i) = "X" Then
names(i) = "Y"